Drop-tube boiler



(No Model.)

J. DEMAREST. DROP TUBE BOILER.

Patented May'28, 1895.-

JOHN DEMAREST, OF MALDEN, MASSACHUSETTS.

' DROP-TUBE BOILER.

SPECIFICATION forming part of Letters Patent N 0. 539,980, dated May 28,1895.

Application filed December 14, 1894. Serial No. 311783. (No mode-l.) v

To all whom it may concern/i Be it known that I, JOHN DEMAREST, ofMalden, county of Middlesex, State of Massachusetts, have invented anImprovement in Drop- Tube Boilers, of which the following description,in connection with the accompanying drawings, is aspecification, likeletters on the drawings representing like parts.

This invention in drop tube boilers has for its object to simplify theconstruction of the same, and to improve the water circulation in thetubes.

' In my experiments to improve drop tube boilers,I have found that it isunwise to provide fixed paths or courses for the water, .inasmuch asunder varying conditions, the water seeks or pursues different paths,and I have, accordingly, adopted that type of boiler in which the tubesare provided with central division .plates, the water being freetodescend or rise at either side said plate. I find it desirable that thewater rising from the tubes should be prevented from meeting and mixingwith the water just entering the tubes, to thereby avoid agitation andretardation of the circulation and to attain this desideraturn I projectsaid central division plates above the inlet openings at opposite sidesthe same at the top ends of the tube, so that the water rising at oneside said division plates is kept separate from the water descending atthe opposite side.

In the preferred embodiment of my invention, the drop tubes areprojected, in the boiler or header, to a considerable distance above thetube sheet and close to the water level, the inlet openings being cut inopposite sides of the tubes close to the level of the tube sheet, theobject of this preferred construction to be hereinafter fully explained.

My invention also comprehends a peculiar arrangement of fusible orsafety plug to prevent the water being exhausted from the boiler ortubes to the damage of the same. In accordance with this part of myinvention, I arrange a safety or fuse plug, preferably at the bottom endof a drop tube, which latter is also preferably so constructed as tofulfill the office of a circulation tube in the normal operation of theboiler. This tube is extended above the level of the tube sheet or theinlet ends of the remaining tubes if the boiler be a drop tube boiler,in order that its supply of water may be cut off before the others,should the water level fall below the normal line. As soon as the'watersupply is cut off, the water which is trapped in the safety tube isquickly evaporated under the action of the fire beneath, and leaves thetube dry, so that the safety plug blows out or fuses, and permits steamfrom within the boiler or header to be discharged through the safetytube upon and to extinguish the fire, and thereby prevent serious damageto' the boiler or its tubes.

In the drawings, Figure 1, in vertical sec tion, shows a boilerconstructed in accordance with one embodiment of my invention, said ithe boiler is shown arranged, the said apparatus being, however,substantially like.

that shown and described in my application Serial No. 517,635, filedJuly 16, 1894, to which reference may be had, it being understood,however, that my improved boiler is not limitedin its use to this or anyparticular kind of heating apparatus, and it may be used by itself,independent of any hot air heater.

Referring to the drawings, Fig. 1, the boiler proper, or, as I shallhereinafter call it, the

header w, has its bottom or tube sheet w perforated, and itsperforations preferably threaded to receive one or more, preferablyaplurality of drop tubes to of suitable material screwed therein, asshown. These drop tubes are preferably-provided at their lower ends orbottoms with screw or other plugs w In the preferred embodiment of myinvention shown in Figs. 1 and 2, the tubes to are projected verticallyabove the tube sheet within the header w, and, for the best results, toa level close to the normal water level within the header, indicatedi-in dotted lines Fig. 1, the said tubes terminating at such a distancebelow the water le'velas to provide proper margin for the usualvariations in the water level in the normal operation of the boiler, itbeing necessary, for the best results, that the ends of the tubes bealways covered by the water. Within the header, and close to the tubesheet w, the drop tubes are provided at opposite sides, in suitablemanner, with inlet openings w, and within the said tubes and betweenthese inlet openings are arranged the preferably central division plates10 which latter extend nearly, but not quite, to the plugs closing theends of the tubes. As herein shown, the division plates L05 are flangedat their edges, as indicated at w and sprung into the tubes, theresiliency of the metal in itself being normally sufficient to retainthem in position, or they may be brazed or otherwise suitably securedwithin the tubes, if desired. These division plates may terminate at thelevel of the inlet openings, but they are preferably extended verticallyabove the said openings, and, in the construction Figs. 1 and 2, theyare shown extended quite to the tops of the tubes.

The operation is as follows, viz: Assuming the header and tubes to befilled with water to the level indicated in dotted lines, when the fireis started in the fire-pot beneath the drop tubes, the latter are heatedand the water within the same begins to circulate, it entering throughone of the openings w in each tube, descending at that side the divisionplate to the bottom of the tube, and rising at the opposite side of thedivision plate, establishing a thorough and strong circulation of watercalculated to generate steam in a short'spaice of time. I'have foundthat under the action of the usual fire, the Water descending at oneside the division plate, and rising at the oth er side, is impelled atsuch speed that it will shoot past the side opening 211 at said other[side and issue at the top of the tube, 'very little of the waterescaping through the said side opening as it rises, so that the waterwhile taken from a level close to the tube sheet, is delivered at ahigher level nearly that of the water line within the header. This is ofgreat advantage, for where the water is delivered into the header closeto the point at which the water enters the tube in its descent withinthe latter, there is apt to be great disturbance, which retards theproper circulation of the water and makes an objectionable noise'.

I prefer to carry the tube end above the tube sheet for the reasonsspecified, but good re sults maybe obtained by a construction, such forinstance as is illustrated in Fig. 3, wherein the tube is terminated atalevel with the top or inner face of the tube sheet, the division plate,however, being extended to a consider able distance above the end of thetube to prevent, to a large extent, the mixing of the in flowing and theoutfiowing water at the tube end.

Referring now to Fig. 1, I have shown the central tube t as droppedslightly below the others to enable it to be more easily distinguished,and provided, like the others, with a central division plate 10 Thescrew plug t at the bottom of the said tube, is, however, provided witha safety or fuse plug 25 and the inlet openings 15 are shown as arrangedat a higher lever Within the header thanthe inlet openings w for theother tubes of the boiler. In the normal condition of the boiler, thewater circulates within the tube 15, precisely as in the remainingtubes, except the water is taken from a higher level than by theremaining tubes. Should the water level, by accident or otherwise, fallbelow the normal, before it can fall to such an extent as to leave thetube sheet dry, it will fall below the inlet openings 25 in the safetytube 25, and will thereby, cut off the said safety tube from its supply,leaving it full of water trapped there in. The circulation in the safetytube being now stopped, the intense heat of the fire quickly evaporatesthe water which is trapped within it, leaving it dry, I having foundthat the water will be completely evaporated from a tube in which thewater is so trapped in a very short time. As soon as the water isevaporated, and the tube left dry, the safety plug 25 fuses and permitssteam from the header to discharge through the safety tube upon and toextinguish the fire before the water level has fallen to such a line aswould leave the tube sheet bare, or cut off the circulation within theremaining tubes.

So far as known to me I am the'first to provide a drop tube with asafety plug located below the tube sheet, and I am also the first, sofar as known to me, to equip one of the regular circulation tubes 'of aboiler with a safety plug in the manner described, whereby it normallyfulfills the function of a circulating tube, and the added function of asafetytube when the water level falls below normal.

My invention is not limited to the particular construction herein shown,for it is obvious the same may be varied without departing from thespirit and scope of my invention.

I claim l. A drop tube boiler comprising a header, one or more droptubes leading from the tube sheet of said header, each provided abovesaid tube sheet with a plurality of inlet openings, longitudinaldivision plates in the respective tubes and arranged between the inletopenings thereof to form alternate paths for the circulating water,whereby the latter may enter either inlet opening, descend at one sidesaid division plate and rise at the opposite side thereof, the saiddivision plate being carried vertically above said inlet openings toprevent intermixing of the inflowing and outfiowing Water incirculation, substantially as described.

2. A drop tube boiler, containinga header, one or more drop tubesextended through the tube sheet thereof, and projected vertically abovethe tube sheet within the said header, and provided close to the tubesheet and below the tube ends with opposite inlet openings atsubstantially the same level; and division plates arranged in therespective tubes,

between said inlet openings to form alternate paths for the circulatingwater, whereby the latter may enter either opening and descend at eitherside the said division plate, rising at the opposite side thereof, saiddivision plate terminating short of the bottoms of the tubes andextended vertically above and between the said openings, substantiallyas described.

3. In a drop tube boiler, the combination with a header, and one or moredrop tubes depending therefrom, of division plates in the respectivetubes and having their edges flanged, as at w, to form hearings tosupport the plates within the respective tubes, substantially asdescribed.

4;. In aboiler, the combination with a header, of a drop tube dependingtherefrom, and a fusible plug in the said tube below the said header,substantially as described.

5. A drop tube boiler, consisting of a header,

and one or more drop circulating tubes communicating therewith, and asafety tube divided to provide a circulation course for the water, andprovided below the said header with a safety plug, substantially asdescribed.

6. In a drop tube boiler, the combination with a header, and a pluralityof circulation drop tubes communicating therewith and provided withinsaid header with one or more inlet openings, of a circulation tube alsoprovided with an inlet opening, but arranged above the level of theinlet openings for the remaining tubes, and provided below saidheaderwith a fusible plug, to operate, substantially as described,

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JOHN DEMAREST.

Witnesses:

. FREDERICK L. EMERY,

M. J. SHERIDAN.

